<template>
  <div class="container">
    <!-- 固定导航 -->
    <van-nav-bar
      fixed
      left-arrow
      @click-left="$router.back()"
      title="小思同学"
    ></van-nav-bar>

    <!-- 聊天主体区域 -->
    <div class="chat-list">
      <div v-for="(obj,index) in chatList" :key="index">
        <!-- 左侧是机器人小思 -->
        <div class="chat-item left" ref="chat-item" v-if="obj.name==='xs'">
          <van-image
            fit="cover"
            round
            src="https://img.yzcdn.cn/vant/cat.jpeg"
          />
          <div class="chat-pao">{{obj.msg}}</div>
        </div>

        <!-- 右侧是当前用户 -->
        <div class="chat-item right" v-if="obj.name==='me'">
          <div class="chat-pao">{{obj.msg}}</div>
          <van-image
            fit="cover"
            round
            :src="userInfo.photo"
          />
        </div>
      </div>
    </div>

    <!-- 对话区域 -->
    <div class="reply-container van-hairline--top">
      <van-field v-model.trim="txt" placeholder="说点什么..." @keydown.enter="sendMsgFn">
        <template #button>
          <span style="font-size: 12px; color: #999" @click="sendMsgFn">发送</span>
        </template>
      </van-field>
    </div>
  </div>
</template>

<script>
import { io } from 'socket.io-client'
import { Notify } from 'vant'
import { mapState } from 'vuex'
// 定义变量，存储 websocket 实例
let socket = null
export default {
  name: 'Chat',
  data () {
    return {
      chatList: JSON.parse(window.localStorage.getItem('chatList')) || [
        { name: 'xs', msg: 'Hi，我是小思，我能帮你什么呢' },
        { name: 'me', msg: '我是编程小王子，我要找老板加薪' }
      ],
      txt: ''
    }
  },
  computed: {
    ...mapState(['userInfo'])
  },
  created () {
    // 1.连接服务器
    socket = io('ws://toutiao.itheima.net', {
      query: {
        token: this.$store.state.token
      },
      transports: ['websocket']
    })
    // 2.监听连接成功事件
    socket.on('connect', () => {
      // 4.接收
      socket.on('message', data => {
        // data就是小思回应的信息
        this.chatList.push({ name: 'xs', ...data })
        // 异步更新
        this.$nextTick(() => {
          this.scrollIntoView()
        })
      })
    })
  },
  watch: {
    chatList (newVal) {
      window.localStorage.setItem('chatList', JSON.stringify(newVal))
    }
  },
  methods: {
    sendMsgFn () {
      if (!this.txt) {
        Notify({ type: 'warning', message: '消息不能为空' })
        return
      }
      // 3. 发送消息
      socket.emit('message', {
        msg: this.txt,
        timestamp: Date.now()
      })
      this.chatList.push({
        name: 'me',
        msg: this.txt
      })
      this.$nextTick(() => {
        this.scrollIntoView()
      })
      this.txt = ''
    },
    scrollIntoView () {
      const chatItems = this.$refs['chat-item']
      // 找到最后一个
      const chatItem = chatItems[chatItems.length - 1]
      // 异步更新
      chatItem.scrollIntoView({
        behavior: 'smooth'
      })
    }
  },
  destroyed () {
    socket && socket.close()
  }
}
</script>

<style lang="less" scoped>
.container {
  height: 100%;
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  background: #fafafa;
  padding: 46px 0 50px 0;
  .chat-list {
    height: 100%;
    overflow-y: scroll;
    .chat-item {
      padding: 10px;
      .van-image {
        vertical-align: top;
        width: 40px;
        height: 40px;
      }
      .chat-pao {
        vertical-align: top;
        display: inline-block;
        min-width: 40px;
        max-width: 70%;
        min-height: 40px;
        line-height: 38px;
        border: 0.5px solid #c2d9ea;
        border-radius: 4px;
        position: relative;
        padding: 0 10px;
        background-color: #e0effb;
        word-break: break-all;
        font-size: 14px;
        color: #333;
        &::before {
          content: "";
          width: 10px;
          height: 10px;
          position: absolute;
          top: 12px;
          border-top: 0.5px solid #c2d9ea;
          border-right: 0.5px solid #c2d9ea;
          background: #e0effb;
        }
      }
    }
  }
}
.chat-item.right {
  text-align: right;
  .chat-pao {
    margin-left: 0;
    margin-right: 15px;
    &::before {
      right: -6px;
      transform: rotate(45deg);
    }
  }
}
.chat-item.left {
  text-align: left;
  .chat-pao {
    margin-left: 15px;
    margin-right: 0;
    &::before {
      left: -5px;
      transform: rotate(-135deg);
    }
  }
}
.reply-container {
  position: fixed;
  left: 0;
  bottom: 0;
  height: 44px;
  width: 100%;
  background: #f5f5f5;
  z-index: 9999;
}
</style>
